The popularity of location-based services has substantially increased in recent years. For example, mobile device users now employ location-based services for navigation, to perform location-based searching, to receive location-based alerts or advertising, to search for or receive notification of nearby acquaintances, and/or the like. Likewise, other parties (e.g., network operators, third-party location-based service providers, remote telemetry users, advertisers, etc.) may employ location-based services to enable emergency services (e.g., E911 services), enable asset tracking or recovery services, provide location-based alerts or advertising, provide notification of nearby acquaintances, perform network registration or billing, and/or the like. The recent increase in the popularity of location-based services has led to the development of many different location determination techniques for mobile devices. Certain location determination techniques may be suitable only for certain kinds of mobile devices and/or certain kinds of radio access networks.
Many different types of radio access networks have been deployed to facilitate radio transmissions to and from mobile devices. As a result, at a single geographic location, a mobile device user may be able to connect to more than one type of radio access network. For example, standing on a street corner, a mobile device user may be able to connect simultaneously to a Global System for Mobile Communications (“GSM”) network and a Worldwide Interoperability for Microwave Access (“WiMAX”) network. In addition, at any single geographic location a mobile device user may be able to access a hard-wired access network, such as a cable network or a landline phone network. Thus, at a certain time point, a mobile device may be located by more than one location determination technique using one or more wired or wireless access networks. For example, at a particular time, a mobile device may be located by a technique suitable for GSM networks (e.g., Uplink Time Difference of Arrival (“U-TDOA”) techniques) and a technique suitable for WiMAX networks (e.g., Assisted Global Positioning System (“AGPS”) techniques).
As a mobile device user moves, the types of available access networks may also change. For example, during the first part of a session, which may include a voice, data, multimedia, location and/or messaging session, a mobile device may only be in range of a GSM network but after its user moves, the device may only be able to access a WiMAX network. Thus, during a single session (e.g., a single voice call) on a mobile device, the location determination techniques available to locate that mobile device may change.